1. Field of the Invention
The present invention relates to a structure mounted with a laminated capacitor (hereinafter, also referred to simply as a mounted structure), which includes a laminated capacitor mounted on a wiring substrate via a joint material.
2. Description of the Related Art
In recent years, with increases in performance of electronic devices, laminated ceramic capacitors as laminated capacitors have been progressively increased in capacitance. In high-capacitance laminated ceramic capacitors, high-dielectric-constant ceramic materials such as barium titanate are used as dielectric materials.
The high-dielectric-constant ceramic materials have piezoelectricity and electrostriction, and therefore will have mechanical distortion generated when a voltage is applied, in the case of laminated ceramic capacitors including dielectric layers of the high-dielectric-constant ceramic materials.
Therefore, when an alternating-current voltage or a direct-current voltage with an alternating-current component superimposed thereon is applied to a high-capacitance laminated ceramic capacitor mounted on a wiring substrate, vibrations will be generated due to mechanical distortion generated in the ceramic material, and the vibrations will propagate to the wiring substrate to vibrate the circuit substrate.
In this regard, when due to the vibrations propagated, the circuit substrate vibrates at a frequency of 20 Hz to 20 kHz in an audio-frequency range, noise referred to as so-called “acoustic noise” will be generated.
Typically, laminated ceramic capacitors have a pair of external electrodes provided on the surface of a body including dielectric layers and internal electrode layers, and the pair of external electrodes is mounted on a wiring substrate by being correspondingly joined to a pair of lands provided on the wiring substrate with a joint material such as a solder. In that case, it is common that the pair of external electrodes mentioned above is provided so as to coat a pair of side surfaces of the body, located to have a separation from each other in a predetermined direction.
Documents that disclose laminated capacitor mounted structures where the laminated ceramic capacitor configured as described above is mounted on a wiring substrate include, for example, JP 2012-151175 A.
In the case of mounting, onto a wiring substrate, the laminated ceramic capacitor provided with the external electrodes to coat the sides of the body as described above via a joint material, the melted joint material will wet upwardly along the outer surfaces of the external electrodes provided to coat the side surfaces of the body, and joint portions will be formed to cover the surfaces of the external electrodes. Therefore, the above-mentioned vibrations generated in the laminated ceramic capacitor will propagate entirely to the wiring substrate through the joint portions formed by the joint material wetting upwardly.
In this regard, in order to reduce the propagation of the vibrations for the suppression of noise generation, it is conceivable that the propagation path for the vibrations is reduced by limiting the amount of the joint material which will wet upwardly in mounting. However, it is extremely difficult to control, with accuracy, the amount of the joint material wetting upwardly in mounting. Therefore, as a result of variations in the amount of wetting upward, the noise generated will also vary significantly, thus making it extremely difficult to stably produce circuit substrates with noise suppressed.